Thanks for the offer of advice Chris but I'm at the collecting tools, scanning ebay and the local ads for a suitable doner at the moment so I'm open to change. I just don't want too much hassle when it comes to the important areas.
Found this if it helps
1988 535 Rear Track 57.501 in | 1460.5 mm.
1993 325 Rear Track 55.701 in | 1414.8 mm.
couldn't find the sierra from the same source
http://www.conceptcarz.com/view/make.aspx
And you quote in another post the sierra rear track was 1460mm
So if I use a shorter rear track can I reduce the length of the wishbones to make it all fit - thus if I use a rear track of 1414.8mm the wish bones will need to be 22.6mm - 10mm (printing error) shorter than stated in the book, leaving a total shorting of the rear wish bone by 12.6mm each side.
I take it that this change wont have a detrimental affect on suspension setup.
Thanks again
Aly